The present invention relates to an image processing apparatus and method, and an image processing system and, more particularly, to an image processing apparatus and method, and an image processing system which performs image processing for forming an image and various image processing on an image inputted from an image input apparatus.
A conventional printer system which forms an image based on image data received from a host computer consists of, as shown in FIG. 1, an image processing apparatus 1 and an image forming apparatus 2.
As shown in FIG. 1, image data sent from an external device 3, such as a host computer, and received by a communication circuit 4 is stored in an image memory 5, which has enough capacity to store one page of image data under control of a CPU 8. Note that a ROM 9 is used for storing programs for the CPU 8, and a RAM 10 serves as a work memory for the CPU 8. Reference numeral 11 denotes a CPU bus connecting the devices described above.
The image forming apparatus 2, for example is an electrophotographic type color printer and has a printer engine 19 which forms an image on the basis of image signals that are read from the image memory 5 and that are processed by various kinds of image processing by an image processing circuit 6. The CPU 8 of the image processing apparatus 1 communicates with a controller 15 of the image forming apparatus 2 via a device side communication circuit 17.
The image memory 5 stores RGB (red, green, and blue) image data, and the image processing circuit 6 converts the RGB data into CMYK (cyan, magenta, yellow, and black) data and sends it to the image forming apparatus 2. The CMYK data depends on toner colors and characteristics of the image forming apparatus 2 to form an image. A conversion function for converting from a RGB color space to a CMYK color space is fixed for each image forming apparatus and is stored in the ROM 9.
A printer system as described above can be constructed by connecting the separately manufactured image processing apparatus 1 and image forming apparatus 2 with an interface cable.
Accordingly, there may be a case where a manufacturer, referred as "a first manufacturer", develops an image forming apparatus 2 and another independent manufacturer, referred as "a second manufacturer", uniquely develops an image processing apparatus 1, then these two apparatuses are connected to form the printer system. In such a printer system, problems arise as described below.
(1) The image processing apparatus 1 manufactured by the second manufacturer may not properly control the image forming apparatus 2 manufactured by the first manufacturer. Under this situation, the image forming apparatus 2 may be damaged. Therefore, there is a possibility that the image forming apparatus 2 will fail earlier than an expected life time of the apparatus when used in a matched configuration.
For example, in the image forming apparatus, the total amount of CMYK color toner to be overlaid is limited to a prescribed amount. An image processing is usually performed so that the total amount of the toner to be transferred onto a recording medium is under the prescribed amount. However, there is a danger that the image processing apparatus manufactured by the second manufacturer may output image data instructing the image forming apparatus to use toners in excess of the prescribed amount. In this case, toner which is not fixed on the recording medium may scatter over the inside of the image forming apparatus, and the fixing unit may be damaged. As a result, the image forming apparatus will not last as long as it is originally designed for.
(2) Especially, when a single color image data is processed with different kinds of image processing relating to colors in different routines which produce a plurality of sets of image data to be outputted, colors of each formed image will differ from those of others. This problem occurs not only in the image forming apparatus but also in the image input apparatus.
Therefore, The image processing apparatus 1 to be connected to the image forming apparatus 2 is desirably manufactured by the same manufacturer as the image forming apparatus 2, or recognizes characteristics of the image forming apparatus 2 if manufacturers of the image processing apparatus 1 and the image forming apparatus 2 differ from each other. Accordingly, a function is necessary which does not allow an undesirable image processing apparatus 1 to be connected to the image forming apparatus 2. As a method for realizing such a function, there is a data scrambling method as described below.
First, the image data is processed in the image processing circuit 6, then applied with a data conversion function f in a data scrambling circuit using a ROM, and is sent to the image forming apparatus 2. The image forming apparatus 2 applies an inverse data conversion function f.sup.-1 to the received image data, and then reproduces the image data. Thus, the data conversion function f is a reversible function, and the image data before conversion and after conversion is the same. The data conversion function f is written in the ROM in the data scrambling circuit of the image processing apparatus 1, and the inverse data conversion function f.sup.-1 is written in the ROM in the data scrambling circuit of the image forming apparatus 2, both as LUTs (look up tables).
By applying the above-described method, the image forming apparatus 2 does not print an image correctly unless scrambled image data is inputted. In other words, the image processing apparatus 1 having a function capable of performing a scrambling process on image data must be connected to the image forming apparatus 2.
However, in the aforesaid apparatuses and system, there are the following problems.
First, since the scrambling function is memorized in the ROM, the function cannot be changed without exchanging the ROMs. Further, when the function is to be changed in an authorized image processing apparatus, it is quite troublesome to exchange the ROMs.
Second, if the conversion function is revealed by way of reverse engineering or the ROM is copied entirely, any image processing apparatus which is not authorized can be connected to the image forming apparatus.
Further, the scrambling function and the method for using same has to be open to an authorized manufacturer, which may cause the secret to be easily, discovered thus causing more problems to the manufacturer.
Similarly for the above-described problem, there is a problem in that image processing parameters used in functions, such as a RGB-CMYK conversion function, in the image processing circuit are fixed for each image forming apparatus and each image input apparatus, and cannot be easily changed. This especially causes a problem when a newly developed image forming apparatus and/or image input apparatus is connected to an authorized image processing apparatus. More specifically, in order to make the image processing apparatus perform image processing suitable for the image forming apparatus and/or the image input apparatus, it is necessary to change ROMs of the image processing apparatus, which is troublesome.